Sorbose properties

Because of similarities in the properties and reactions of sorbose and fructose, Schlubach and Graefe86 suggested that a-L-sorbose is closely related to /3-D-fructose. This was further investigated by Ohle87 who showed experimentally that /3-D-fructose and a-L-sorbose have the same configuration except at C5. Hudson88 has suggested that in /3-D-fructose the hydroxyls on C2 and on C3 are cis. 

Since L-sorbose is a reducing sugar a number of methods for its determination, based on this property, have been reported. Titration with the ceric sulfate, potassium ferricyanide reagent showed a fructose to sorbose ratio of 1.1,86 Cupric citrate87 as well as cupric tartrate87 reagents appear to be equally useful. 

In 1895 Dull,9 who was studying inulin and its products of hydrolysis, found that when either fructose or sorbose was treated with an aqueous solution of oxalic acid under pressure, a substance was obtained which had the formula CeHeOa and resembled furfural in its properties. This substance was further investigated by Kiermayer4 who found that fructose and sucrose were the best sources when they were heated with 0.3% aqueous oxalic acid at 120°. It was however only the fructose portion of the sucrose molecule which was transformed since the glucose moiety was recovered unchanged. Kiermayer prepared several derivatives of CeH Os and from its reactions concluded that its structure was probably /3-hydroxy-S-methylfurfural (III). Van Ekenstein and... 

Interruption of such a reaction at the intermediate stage should provide more-positive evidence for the mechanism proposed. Treatment of inositol cyclase with charcoal removed the NAD, and, when the enzyme was reconstituted, its properties were found to have been modified. By using this preparation, hydrogen from NADH-t was transferred to C-5 of both xyZo-hexos-5-ulose 6-phosphate (59) and L-sorbose 1-phosphate, giving a mixture of D-glucose-5-f 6-phosphate (58) with lL-mi/o-inositol 1-phosphate (61) or D-glucitol-5-f 6-phosphate, respectively.166 This shows that the enzyme can catalyze the partial reaction corresponding to reduction of the oxidized intermediate proposed. 

The CD and conformational properties of acyclic derivatives of fructose, sorbose, tagatose, and four deoxy derivatives of fructose have been reviewed [14],... 

Properties Colorless, crystalline solid. Mp 80C. Hygroscopic soluble in water and alcohol. Derivation Action of sorbose bacterium on glycerol. 

Ohle isolated an isomeric mono-O-isopropylidene-L-sorbose from a similar reaction. After removing diacetal 3, he acetylated the remaining mixture containing monoacetals. Fractional recrystallization of the distilled mixture of triacetates was effected from methanol-water, and, on saponification, one fraction of the crystalline material gave l,2-0-isopropylidene-o -L-sorbopyranose (11) in 3% yield from L-sorbose. Periodate oxidation of 11 showed consumption of two moles of oxidant per mole, with formation of one mole of formic acid. The monoacetal 11 was also isolated in 16% yield when a suspension of L-sorbose and copper(II) sulfate in impure acetone was shaken for seven days. Other products were 3 and an isomeric di-O-isopropylidene-L-sorbose which was obtained in 1% yield and regarded by Ohle as slightly impure. Its properties (m.p. 155-157°, [aJu -f-44.9° in acetone) closely match those of l,3 4,6-di-0-isopro-pylidene-j8-L-sorbofuranose (18) (m.p. 159-160°, [a]i)-f-43.4° in acetone), identified by Maeda in 1967. Patil and Bose later isolated, but did not identify, a diacetal which was probably 18 (m.p. 155-157°, [a]n -f-4.49° in acetone). 

Table 3.5 Catalytic properties of L-sorbose oxidation with Pt-containing nanostructured catalysts 1 . ...

As can be seen from Table 3.5 ( 4), Pt nanoparticles formed in HPS are more selective in L-sorbose oxidation than the catalysts based on block copolymers but still the selectivity is not sufficient We believe that low selectivity may be attributed to saturation of the nanoparticle surface with H2 during reduction, which alters the sorption-desorption equilibria of the L-sorbose, oxygen and 2-keto-L-gulonic acid [89]. As was demonstrated in Ref [96], L-sorbose oxidation can be catalyzed not only with Pt(o) but also in the presence of Pt ions. This prompted us to investigate the catalytic properties of HPS-Pt without Pt ion reduction. 

The Pt-containing (2-4% Pt) nanocomposite beads placed in an aqueous basic solution of L-sorbose catalyze oxidation of the latter with O2 to 2-keto-L-gulonic acid, an intermediate in the production of vitamin C [399]. Within first 100 min at 60—80°C the catalytic activity gradually develops, resulting in a 100% convenion of L-sorbose with the yield of ketogulonic acid up to 98% [400]. With the size of Pt clusters controlled by the size of matrix network meshes, the catalytic properties of the composite material remain stable even after 30—50 reaction cycles... 

One has only to think of the extraordinarily varied metabolic functions of thiamine, riboflavin, pantothenic acid, pyridoxine, and biotin to realize that it is most unlikely that ascorbic acid could possibly replace every one of these. Moreover, one would have to postulate a quite different mechanism for the large number of other substances, such as sorbitol, sorbose, arabitol, and starch, which spare B vitamins even more readily than ascorbic acid, but which do not have its redox properties. 

An investigation of the properties of the newly discovered l>ketose-3-epiinerase (see Vol. 27, Chapter 2, Ref S3) now named D-tagatose-3-epimerase, showed that it is most active on 3,4-cis configurated substrates, establishing a 30 70 cis/trans equilibrium. Thus the rare sugars D-sorbose and D-psicose have become available from >-tagatose and D-fhictose, respectively. ... 

Zhao, S.G., Yao, L.M., Su, C.X., Wang, T. et al (2008) Purification and properties of a new L-sorbose dehydrogenase accelerative protein from Bacillus megaterium bred by ion-beam implantation. Plasma ScL Technol, 10, 398-402. 

Here we discuss Pt and Ru compound NPs (no reduction) formed in block copolymers and HPS in catalytic oxidation of L-sorbose and D-glucose (Fig. 2). Table 2 shows catalytic properties of these nanocomposites. 

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